Expansion tank

[French Frie]

Hi all,
   
   I finally changed my thermostat, as my engine didn't warm up correctly... I tested the old thermostat, and found that even if it opened in boiling water, it didn't close fully when cooling ! It was seized...
   By the way, it's a mess to take out the thermostat housing on the 5.0, and an even bigger mess to put the lower bolt back, as the water pump casting fouls its screwing !  Little trick : i eventually used a saw to make a slot in the bolt head,in order to use a screwdriver passing through belts to make the bolt finding its path...
   
   It's far better now, even though my fan still cuts in too early ...
   
   But now a new wonder arises :  i had a look at the expansion tank, to find out that it is only connected to the upper radiator pipe, AFTER the pressure cap ... It means that it only collects overflow water, when pressure cap has opened, and that there is no way to make this water go back to the circuit when it get colder ! I understand now why the level was always the same, cold or hot !
   It is by the way more an overflow tank than an expansion tank ... I assume other MKIVs have the same configuration?  So how to know that the coolant level is ok , as the level on the tank is irrelevant ?
   
   I think i'll make a derivation in one of the water pipe that goes to the butterfly or to the heater, to make a "true" expansion tank... has anyone already done this ? I've read in Sept '12 ACtion that Nick Godridge modified his coolant system, IIRC...
   
   Thanks !
   
   Olivier

[dkp_cobra]

Hi Olivier,
   
   I use a Corvette C2 expansion tank:
   
   
   
   Peter

[French Frie]

I remember that, Peter... and, I stand to be corrected, you suppressed the pressure cap on the upper pipe as well ? where is (are) the inlet (outlet) pipe of the exp tank connected ?
   
   but If I'd change the tank, I assume I'd replace it with a SBF adaptated Fairlane expansion tank, like on the 427s, fitted directly on the thermostat housing ...
   
   thanks !

[dkp_cobra]

Olivier, you are right. I removed the old pressure cap and use the one from teh expansion tank. The inlet of the expansion tank is connected with the overflow of the radiator. The outlet of the expansion tank is connected with the water pump. The right pipe of the expansion tank pointing to bottom is connected with nothing. Normally, no water is floating through this pipe.

[French Frie]

Peter, you're talking about  an overflow from the radiator... But I have no other connection than the upper and lower pipes on mine ! I also notice by watching your pics that your fan switch seems to be screwed in rather than just pressed in, as in ours... Is it stock or did you modify it ?
   
   By the way, who knows  where is the MKIV radiator from ?

[dkp_cobra]

quote:Originally posted by French Frie
   
Peter, you're talking about  an overflow from the radiator... But I have no other connection than the upper and lower pipes on mine ! I also notice by watching your pics that your fan switch seems to be screwed in rather than just pressed in, as in ours... Is it stock or did you modify it ?
   
   By the way, who knows  where is the MKIV radiator from ?
   

   
   Olivier, I forgot but you are right. The overflow at my radiator is a modification.

[westcott]

Olivier,
   
   if possible go with the stainless variant for the FE tank, they are much better. The brass tanks don't like too much pressure and will leak from time to time.
   
   I used brass tanks on my Clevelands and FE engine.

[French Frie]

Hi Uwe,
   
   thanks for the tip ! and how is your set up  ? do you have and additional pickup on the radiator, like Peter, or did you use the heater circuit ?

[French Frie]

PS : no idea for the origin of the stock radiator ? any alloy replacement part ? thanks !

[nick Godridge]

Yes I did and its seems to work well.
   
   Done by Historic Automobiles in Petersfield, who race both Cobra's and GT40's.
   It was simple a round swirl pot type tank attached to the inner wing in the same place you have placed the header in your pic.
   The tank was then connected to both the top and bottom steel pipes.
   
   Would post pic, but can not figure out how to do it.!!
   
   Whilst we are on the subject I would still like to increase the water flow ate low revs, thoughts anyone.??
   
   Nick g

[French Frie]

Hi Nick ! Thanks for your input... Pic welcome !
   
   For your wish, the easiest would be smaller pulley, in order to make the pump turning faster, but attention has to be paid for cavitation risk at high revs ... Other solution : "racing" water pump, but more complicate to change, and cavitation risk can be present as well (but  unobvious under 6k rpm, i assume).

[westcott]

Hi Olivier,
   
   the FE expansion is connected directly to the thermostat housing and therefore dosn't need any connection to the pump or heater circuit.
   
   The bigger hose goes directly to the radiator upper connection, one additional air evacuation hose from upper half of the expansion tank to upper radiator water tank is needed if not in place.

[westcott]

My radiator has a badge "Serck of London" on it like the 60s radiators.
   
   There are Fluidyne radiators in Ebay supposed to be direct replacements for the original brass radiator.
   
   Martin aka Hobo here ordered one for his "Sleeping Beauty" project maybe he can send you some measurements go compare with your brass radiator.
   
   You can find them here:
   
   http://www.ebay.de/itm/350370888166?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
   
   For my "Frog's" 331 engine build i decided on the March Street Rod Pulley Kit # 30105 with high water flow ratio and never had any problem till now.
   
   If you don't want to change your setup too much just install a round or other shaped higher volume expansion tank at a higher position and connect it as your original tank to increase the total water volume of your cooling circuit.
   
   It will definitely help as Nick said before.

[nick Godridge]

Sorry FF apparently you need to run a photo sharing account with someone like Picassa to share stuff on this forum.
   
   Not up for that I'm afraid, seems a bit unescesary to me.
   
   Am happy to email you stuff if you wish. Contact me on nick@ngodridge.com.
   
   Nick G

[French Frie]

Nick, email sent !